I'm developing a system using Code Ignitor framework.When a user login to the system, it keeps user profile in session as general way.Sometimes users report me that, they can see "someone else profile", and when change page, it becomes normal, and some times, they can see someone else profile again.

This problem is found only some times, but it is really not good. I cannot specify the cause, because session system in the framework should be well-design. I also wonder that for systems those require high-certainty such as online banking, how do they manage this issue.

It's easier to help you find what you're doing wrong if we see what you're doing... Just saying we could brainstorm all day and we're not going to land on an unterminated string literal without seeing the code.